Insights into lunar visibility, Islamic calendar precision, and the science of the crescent.
Moonrise comes on average 50.5 minutes later each day, so about once a month a calendar day has no moonrise at all, and another has no moonset. In 2027 Mecca, London, Istanbul, Karachi, Jakarta, New York and Cape Town each have 12 of each; the day without a moonrise falls near the last quarter. In Tromsø the Moon stays up or down for whole days, up to eight in a row.
The faint glow on the dark part of a young Moon is earthshine: sunlight reflected by the Earth onto the Moon's night side. Seen from the Moon, the Earth's phase is the reverse of the Moon's, so a thin crescent faces a nearly full Earth, 3.7 times wider than the Moon and about 49 times brighter than our full Moon. By first quarter the earthlight has fallen to 30 per cent of its new-moon strength.
The Hijri calendar for 2027: the first day and length of every Umm al-Qura month that falls in the year, the Islamic New Year 1449 on 6 June, Ashura on 15 June, the Mawlid on 14 August, two Isra and Mi'raj dates, the nights of Laylat al-Qadr and the white days of every month.
The expected first day of Ramadan and of Eid al-Fitr for every year from 2027 to 2035 (1448 to 1457 AH) by the Umm al-Qura calendar, the new moon before each Ramadan, whether the crescent can be seen on the 29th of Sha'ban, and why Ramadan comes about 11 days earlier every year.
A Hijri year is 11 days shorter than a Gregorian one, so you are one Hijri year older from about your 33rd birthday. Enter your date of birth to see your Hijri date of birth, your age in Hijri years and your next Hijri birthdays, and learn why a year can hold two of them.
The Hijri year number gains one year on the Gregorian count every 32.6 years. The gap is 578 from the Hijri New Year to 31 December and 579 from January until the next one, so the two numbers meet around 20,841 to 20,874 CE. Here is the arithmetic, a chart, and why the answer is only an estimate.
The picture of a crescent beside a bright star happens in the real sky, when the young Moon passes Venus or Jupiter in the evening twilight. Seen from Mecca it happens on 16 evenings from October 2026 to 2030. The closest is 30 November 2027, when the crescent stands 1.3 degrees from Venus, and in early 2028 the crescent passes Venus every month from January to May.
Ramadan moves about 11 days earlier every year and goes once round the seasons in about 33 years. We computed the daylight of every Ramadan from 2026 to 2059 in five cities: in London it swings from 7.9 hours in 2032 to 16.6 hours in 2049; near the equator it hardly changes.
A supermoon is a full moon near its closest to the Earth, a micromoon one near its farthest, and a blue moon the second full moon of a calendar month. Of the 124 full moons from 2026 to 2035, 25 are supermoons and 16 micromoons; the closest, on 25 November 2034, looks 14 per cent wider than the farthest. None of them changes the Islamic calendar.
Ten lunar eclipses fall between February 2027 and December 2030, three of them total. We worked out how much of each one London, Istanbul, Cairo, Mecca, Tehran, Karachi, Dhaka, Kuala Lumpur and Jakarta will see, and when.
The Moon's orbit wobbles once every 18.6 years: at a major standstill, like 2024 and 2025, it swings to 28.7 degrees north and south of the equator; at a minor one only 18.6. The same wobble raises or lowers the new crescent. At 45 degrees north, the 24-hour-old Moon of August to October averages only 0.5 degrees above the horizon at sunset from 2024 to 2031, against 6.7 in 2035 to 2040.
On the same evening a 24-hour-old Moon is a bowl at 30° N and almost on its end at 45° S. At 45° N it averages 9.9° high in March but 2.7° in October. We computed 619 new moons to show how latitude and season set the tilt and height of the crescent.
We computed the crescent at Mecca on the evening before each of 300 Umm al-Qura months (1423 to 1447 AH). In seven months out of ten it was below the visibility threshold for any method, and the Moon was younger than the naked-eye record in more than half. What the rule says, what the numbers show, and what they do not mean.
The tabular Hijri calendar repeats every 30 years, with 11 leap days. Why 30 and not 8, 19 or 79? We tested every cycle up to 100 years against the real lunar month: 30 is the first to come within 17 minutes, and the calendar then drifts a day in about 2,500 years.
The Moon passes within half a degree of straight overhead at the Kaaba between 5 and 19 times a year, but not once from 2032 to 2036, because of the 18.6-year cycle of the Moon's path. The full moon can only do it between October and February; the next time is 13 November 2027, at 23:44 Mecca time.
Some Gregorian years contain two Eid al-Fitr or two Eid al-Adha. The last were 2000 and 2006; the next are 2033 and 2039. Why it happens, the full table, and which years are borderline.
Mecca sees totality on 2 August 2027. NASA's path tables put the next one on 5 February 2334, with Mecca inside the path by only about 7 km. Medina waits until 2114. How to tell whether a city is inside the path, the near misses, and why a forecast 300 years ahead cannot be trusted to the kilometre.
We placed every solar and lunar eclipse from 2024 to 2035 on the Umm al-Qura calendar. Solar eclipses cluster on the 29th, lunar ones on the 14th and 15th. Here is the reason, and what changes if the day starts at sunset.
Every solar eclipse has a lunar partner about two weeks away, and every lunar eclipse a solar one. The Moon's orbital nodes explain why, with real dates from 2026 to 2030, the triple of August 2027 and the Saros arithmetic.
The Moon takes 27.32 days to circle the stars, 27.21 to return to its node, 27.55 to return to perigee and 29.53 to go from new moon to new moon. Which month runs the Hijri calendar, eclipses and the supermoon cycle, and why even the 29.53 days varies.
Twice a year the Sun stands straight over the Kaaba, on 27 or 28 May at 09:18 UTC and on 15 or 16 July at 09:27 UTC. At that minute, wherever the Sun is up, an upright stick's shadow points directly away from Mecca, and facing the Sun is facing the Qibla to within a fifth of a degree. The Americas get two more chances in January and November.
An annular solar eclipse falls on 6 February 2027, two days before Ramadan 1448 is expected to begin. Where it can be seen, why it cannot be seen from Mecca, and what it tells us about the crescent.
On 2 August 2027 a total solar eclipse crosses Egypt and Saudi Arabia. Mecca and Jeddah are inside the path of totality, Medina is not. Exact local times, durations for each city, and how to watch safely.
A complete guide to moon sighting: what it is, why it begins each Islamic month, the science of crescent visibility, why countries differ, and how to observe the hilal yourself.
The Moon sweeps from a high arc to a low one across the sky in just two weeks, while the Sun takes six months. Here is the astronomy behind the Moon's monthly arc cycle, and how to watch it in the Sky Dome.
Understand moon phases through phase angle, elongation, and illuminated fraction -- and how the geometry of each phase connects to crescent visibility, the Yallop q-value, and when the hilal appears.
A scientific deep dive into how Earth's atmosphere bends light near the horizon, how temperature and pressure alter the Moon's apparent position, and why refraction and extinction quietly reshape the numbers that feed crescent visibility models.
Can you see the crescent moon with the naked eye? Learn which Yallop zone needs which equipment, plus the best binoculars and telescopes for hilal hunting.
A scientific exploration of how observer elevation, horizon obstructions, and local topography dramatically affect crescent moon visibility, from horizon dip geometry to the physics of atmospheric extinction, and why hilltop observers consistently outperform those at sea level.
A scientific explanation of why the new crescent moon can be sighted in one country while remaining completely invisible in another, even on the same evening. Covers the role of longitude, latitude, the sunset sweep, moon age, and the geometry that creates global visibility zones.
When is Eid al-Fitr 2027 and Eid al-Adha 2027? Crescent forecasts, the likely dates, Arafah, and why your country may differ by a day.
Understanding the differences between Astronomical, Umm al-Qura, and Tabular calendar calculations, why they disagree, and how to read all three at once.
Everything you need to know to successfully observe the new crescent moon, from choosing the right location and timing your observation window, to scanning techniques used by expert hilāl hunters.
Master crescent observation and moon sighting scoring on moonsighting.live: Yallop zones, points, ranks, badges and worked examples. Build your log today.
A deep dive into the Danjon Limit, the hard physical boundary below which the crescent moon becomes invisible regardless of telescope power. Explore the lunar topography, optics, and modern CCD observations that define the absolute edge of crescent visibility.
How the Umm al-Qura calendar works, its exact astronomical rule since 1423 AH, why it does not guarantee crescent visibility, and the recurring Ramadan controversies.
Learn how to photograph the crescent moon with the right camera, lens and exposure settings, plus daytime infrared technique, stacking and safe Sun avoidance.
A comprehensive guide to the hilāl, the thin crescent moon that determines the start of every Islamic lunar month, from its Quranic origins to the modern astronomy behind predicting its visibility.
A journey through 4,000 years of crescent moon observation, from ancient Mesopotamian astronomers who recorded lunar data on clay tablets, through medieval Islamic scholars who built the first visibility theories, to modern CCD cameras and crowdsourced global networks.
Watch global moon sighting reports roll in live on the 29th night. Discover how sunset sweeps east to west, giving western observers extra elongation and turning a local act into a planet-wide wave.
Who saw the youngest crescent moon ever? Verified naked-eye, optical-aid and photographic records, from O'Meara to Legault, with the science of how thin a hilal can be.
A deep dive into how Hilal Vision predicts the visibility of the new crescent moon using the Yallop q-value and Odeh V-value criteria, ARCL, crescent width, and the Danjon limit.
How the Islamic Crescents' Observation Project collects, cross-checks, and publishes crescent sighting data, how the 1,028 reports from 1440 to 1446 AH in the Hilal Vision archive are organised, and what they reveal about the Yallop and Odeh models.
Ramadan 2027 (1448 AH) is expected to begin on Monday 8 February 2027. Here is the verified moon-sighting geometry, why the date is a forecast and how to track it live.
Why do Muslims start Ramadan on different days? A clear, sourced guide to global vs local moon sighting, calculation, the Saudi declaration and the science of disputes.
An objective, scientifically grounded analysis of the longstanding debate between physical moon sighting and astronomical calculation for determining Islamic months, examining the evidence, accuracy, and limitations on each side.
A researcher-grade guide to global versus local moon sighting (matla): the fiqh of ittihad and ikhtilaf al-matali, Wujud al-Hilal vs Imkan al-Rukya, and unified calendar proposals.
An in-depth exploration of the Islamic Hijri calendar, how lunar months are determined, why there are multiple systems, and the science behind the ongoing debate between astronomical calculation and physical sighting.